1. Technical Field
The present invention generally relates to a semiconductor memory device and a method of controlling the same, and more particularly, to a semiconductor memory device including a write driver and a method of controlling the same.
2. Related Art
According to a need for an increase in the capacity and speed of semiconductor memory devices and a reduction in the power of semiconductor memory devices, researches are being carried out on the next-generation memory devices which can embody the high degree of integration and low consumption power of DRAM devices, the nonvolatile property of flash memory, and the high-speed operation of SRAM. The next-generation memory devices that are now being in the highlight include phase change random access memory (PRAM) using a phase change material, resistance random access memory (RRAM) using material having a variable resistance characteristic, such as transition metal oxides, and magnetic random access memory (MRAM) using ferromagnetic material. Common points in the materials of the next-generation memory devices are that the resistance values of the materials are varied depending on the size and/or direction of a current or voltage, the materials have a nonvolatile characteristic in which the resistance values of the materials remain intact even when a current or voltage is cut off, and the materials do not need to be refreshed.
A unit memory cell of this resistive memory device can include one resistance element and one switch element. Data is stored by changing the resistance of each resistance element by controlling the current or voltage of a word line and bit line connected to memory cells.
The write driver of this phase change memory device is described below. A current is supplied using a high voltage and the gate bias voltage of a PMOS.
When a word line is enabled in response thereto, a current supplied from the write driver is transferred to a memory cell. Line resistance, the resistance component of a switch element, etc. are inevitably generated in a current path.
Accordingly, the write driver may need to supply a larger amount of current according to circumstances. In contrast, when a common amount of current is supplied to a memory cell, data to be written may not be properly written.